Back in the good old days, when I bred chameleons for a living, I made quite an effort to understand this. UV and D3 metabolism is not an easy task,,,,,,,,,,
Why use UVB? This is the first question you have to ask yourself. UVB is used becorse study after study have shown that diffrent calcium related condisions occour if humans, reptiles, corals etc are not exposed to UVB. When exposed we and many other living things produce vitamine D3, this vitamin is then used in the body so we can absorbe calcium in the metabolism to build scletton, eggs, whatever.
The problem with this is that it´s just an absumtion, we do not understand how this works. Why do some spices get MBD and some not?
The key is D3. If you can provide enough D3 by feeding or some other way the problem seam to disapear even without UVB.
But D3 is a tricky little ****er,,,,,,,it gets old, it´s non sticky, etc.
SO.....if you are not shure about if you are giving your animals enough D3, do not walk on the wild side, provide UVB. If you got a potent D3 sourse skip the UVB.
Forget about comercial reptilevitamines as a D3 sourse, you´ll need something moore potent, look at the birdindusty products etc.
I rasied hundreds of chameleons each year for many years without a single UVB-ray but with lot´s of D3. They same goes for any reptile but some need moore. Strops, F.pardalis etc probably need a lot.
Sorry about my bad english,,,,,you boys should try Swedish;-)